This invention relates to a method of and apparatus for forming projections on tubular members or the like and, more particularly, to the formation of such bulged articles by an apparatus which rotates with respect to the article being formed.
Heretofore it has been known to form projections on tubes by various means including the use of cooperatively shaped rollers one of which is inserted within the tube to be formed while the other engages the exterior of the tube. Such a system is objectionable not only because of the slowness of this arrangement but also because of the difficulty in controlling the rollers as distance from the origin of the driving force to the point of application to the tubular member increases.
Another approach to the problem has been to substitute a shaped or grooved mandrel for one of the cooperatively shaped rollers. One advantage in this approach is that a plurality of exterior rollers may be employed in unison to increase the speed of formation. A principal disadvantage of this approach, however, is that the mandrel must be quite massive to provide suitable rigidity. The system lacks versatility in that substantially only a single product can be produced with a given mandrel. It is also quite expensive to employ this system.